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<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Lots of Objects - Merged w/vertex colors</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import * as BufferGeometryUtils from 'three/addons/utils/BufferGeometryUtils.js';
import {OrbitControls} from 'three/addons/controls/OrbitControls.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  const fov = 60;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 10;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.z = 2.5;

  const controls = new OrbitControls(camera, canvas);
  controls.enableDamping = true;
  controls.enablePan = false;
  controls.minDistance = 1.2;
  controls.maxDistance = 4;
  controls.update();

  const scene = new THREE.Scene();
  scene.background = new THREE.Color('black');

  {
    const loader = new THREE.TextureLoader();
    const texture = loader.load('resources/images/world.jpg', render);
    const geometry = new THREE.SphereGeometry(1, 64, 32);
    const material = new THREE.MeshBasicMaterial({map: texture});
    scene.add(new THREE.Mesh(geometry, material));
  }

  async function loadFile(url) {
    const req = await fetch(url);
    return req.text();
  }

  function parseData(text) {
    const data = [];
    const settings = {data};
    let max;
    let min;
    // split into lines
    text.split('\n').forEach((line) => {
      // split the line by whitespace
      const parts = line.trim().split(/\s+/);
      if (parts.length === 2) {
        // only 2 parts, must be a key/value pair
        settings[parts[0]] = parseFloat(parts[1]);
      } else if (parts.length > 2) {
        // more than 2 parts, must be data
        const values = parts.map((v) => {
          const value = parseFloat(v);
          if (value === settings.NODATA_value) {
            return undefined;
          }
          max = Math.max(max === undefined ? value : max, value);
          min = Math.min(min === undefined ? value : min, value);
          return value;
        });
        data.push(values);
      }
    });
    return Object.assign(settings, {min, max});
  }

  function addBoxes(file) {
    const {min, max, data} = file;
    const range = max - min;

    // these helpers will make it easy to position the boxes
    // We can rotate the lon helper on its Y axis to the longitude
    const lonHelper = new THREE.Object3D();
    scene.add(lonHelper);
    // We rotate the latHelper on its X axis to the latitude
    const latHelper = new THREE.Object3D();
    lonHelper.add(latHelper);
    // The position helper moves the object to the edge of the sphere
    const positionHelper = new THREE.Object3D();
    positionHelper.position.z = 1;
    latHelper.add(positionHelper);
    // Used to move the center of the cube so it scales from the position Z axis
    const originHelper = new THREE.Object3D();
    originHelper.position.z = 0.5;
    positionHelper.add(originHelper);

    const color = new THREE.Color();

    const lonFudge = Math.PI * .5;
    const latFudge = Math.PI * -0.135;
    const geometries = [];
    data.forEach((row, latNdx) => {
      row.forEach((value, lonNdx) => {
        if (value === undefined) {
          return;
        }
        const amount = (value - min) / range;

        const boxWidth = 1;
        const boxHeight = 1;
        const boxDepth = 1;
        const geometry = new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth);

        // adjust the helpers to point to the latitude and longitude
        lonHelper.rotation.y = THREE.MathUtils.degToRad(lonNdx + file.xllcorner) + lonFudge;
        latHelper.rotation.x = THREE.MathUtils.degToRad(latNdx + file.yllcorner) + latFudge;

        // use the world matrix of the origin helper to
        // position this geometry
        positionHelper.scale.set(0.005, 0.005, THREE.MathUtils.lerp(0.01, 0.5, amount));
        originHelper.updateWorldMatrix(true, false);
        geometry.applyMatrix4(originHelper.matrixWorld);

        // compute a color
        const hue = THREE.MathUtils.lerp(0.7, 0.3, amount);
        const saturation = 1;
        const lightness = THREE.MathUtils.lerp(0.4, 1.0, amount);
        color.setHSL(hue, saturation, lightness);
        // get the colors as an array of values from 0 to 255
        const rgb = color.toArray().map(v => v * 255);

        // make an array to store colors for each vertex
        const numVerts = geometry.getAttribute('position').count;
        const itemSize = 3;  // r, g, b
        const colors = new Uint8Array(itemSize * numVerts);

        // copy the color into the colors array for each vertex
        colors.forEach((v, ndx) => {
          colors[ndx] = rgb[ndx % 3];
        });

        const normalized = true;
        const colorAttrib = new THREE.BufferAttribute(colors, itemSize, normalized);
        geometry.setAttribute('color', colorAttrib);

        geometries.push(geometry);
      });
    });

    const mergedGeometry = BufferGeometryUtils.mergeBufferGeometries(
        geometries, false);
    const material = new THREE.MeshBasicMaterial({
      vertexColors: true,
    });
    const mesh = new THREE.Mesh(mergedGeometry, material);
    scene.add(mesh);
  }

  loadFile('resources/data/gpw/gpw_v4_basic_demographic_characteristics_rev10_a000_014mt_2010_cntm_1_deg.asc')
    .then(parseData)
    .then(addBoxes)
    .then(render);

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  let renderRequested = false;

  function render() {
    renderRequested = undefined;

    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }

    controls.update();
    renderer.render(scene, camera);
  }
  render();

  function requestRenderIfNotRequested() {
    if (!renderRequested) {
      renderRequested = true;
      requestAnimationFrame(render);
    }
  }

  controls.addEventListener('change', requestRenderIfNotRequested);
  window.addEventListener('resize', requestRenderIfNotRequested);
}

main();
</script>
</html>

